Time is a limited resource

Recently I needed to extract a hand drawn object, like a child's doodle, from a camera image. The method that I found to be working reasonably good was OpenCV's EM (Expectation Maximisation) method. The idea is that there will be pixels that are "close" enough that they are classified as one group, and hopefully with a doodle on paper, the algorithm will be able to cluster the colored pixels together against the white background of the paper. First, I tried the algorithm on a random image and classifies it into three clusters. The result is as follows. Hmm...looks good. The bright areas, almost white, are classified into one cluster (blue), whereas the darker and lighter colors are classified into two other clusters (red and green). So what happens when used on a hand drawn doodle, and clustering it to two clusters (two separate background and desired object) ? Not bad at all. There are some "holes" inside the contour since the coloring does n...

I have been recently working on projects that use the Microsoft Kinect, and also had the chance to use OpenCV to calibrate the color camera in the Kinect. This is because one of the projects use Aruco AR markers and to obtain the orientation of the Aruco markers, we need the camera's internal parameters and therefore, calibration! The Kinect's camera is just like any other webcam, so there is nothing special about it. But I thought the calibration process can help others who are just starting to use OpenCV and need to get camera internal parameters. The code can be found here . You need to prepare a calibration board with checker patterns with known length. The pattern image is also included in the repository but you'll need to find a sturdy planar object such as a wooden board. Currently there is not any UI so it's probably good to share here that after you position your checker board you need to manually press 'c' to capture an image. Repeat this 10 ti...

So recently I need to find a way to get two Unity projects on different machines talking and sharing data. The data shared is nothing like multiplayer games, far from it, it was just a notification of an event flag that became true on one machine. So if a special event happens on one machine then the other machine will also know. This is just sending a string or an int as a flag, simple! My first attempt was to use Unity's Unet Multiplayer Networking system. It looks easy enough to use right ? So I followed the Networking tutorial here . Turns out it was not as smooth as I'd hoped... The server only works as standalone. So we need to build the application and run as standalone. Not a big problem, but for those who don't read the manuals (like me, hehe) this is the first obstacle. Just running on the Editor will not work. However, it does not work between computers. I was running a mac and a windows machine and although they could see each other just fine (ping worked)...

Unity is a fabulous tool for not only games but also interactive entertainment, simulations, etc. And there are many good tutorials on tips and tricks to optimize performance and code readability. I compiled this list as a memo to myself when starting out on Unity, so I can always refer back to the basics and hoping that this can help someone else too. Object pooling. Object pooling is a pretty cool trick and it improves performance because you can reduce the number of Initiate() and Destroy() calls. To illustrate why Destroy can be bad, I attached a screenshot of a project I was building with Unity. I'm not going to go into the details of Object Pooling because there are already many good tutorials out there. One of them being this one.  One thing to always keep in mind is that it is easy to get MissingReferenceException if you accidentally Destroy() the pooled objects. It happened to me once where I attached one script to multiple prefabs which behave the same except that so...

個人メモ。しばらくWindows 8 でURGセンサを使っていたが、新しいPC に開発環境を構築することになった。そして、Visual Studio を入れたらVisual Studio 2017 に新しくなった！ とりあえず ここから URGライブラリをダウンロード。 解凍してビルドしたらエラー。ビルドターゲットは古いWindows SDKに設定されているようだな。ソリューションを右クリック、「ソリューションを再ターゲット」を選択する。そしたらもう一度ビルド。今回はうまくいった！ Debug とRelease 両方ビルドすることをお忘れなく。

So after about 7 years I recently started playing around with OpenCV again. It really has come a long way especially on how it distributes binaries and libraries. I still remember the old days when building on Linux was hard but possible whereas Windows was short of impossible. Well it seems that has all changed ! After struggling to build this new version of OpenCV for about 2 days I decided to share it here for my own memo and hopefully it can also help others who need it. This is heavily based on  this tutorial . Let's dive in. First things first. We need to make sure we have a similar build environment. Windows 10 Visual studio express 2015 Opencv 3.1 Dependencies  : Just choose what you need. Step 1 Download OpenCV executable  here . You will find it in your Downloads folder. Run it and you will get an opencv folder. Feel free to move it around to any path you like. Let's assume it is in {opencv_dir}. In my case, as you can see from the screenshot, I m...